Good question, Soil Margin!
Because most LED fixtures are configured into flat/horizontal panels, they do tend to lend themselves better to horizontal grows, providing an even spread of light across the canopy...
...BUT, with a little creative ingenuity, LED fixtures can be configured for vertical use. There are a couple of folks I've seen doing vert LED grows, but they're usually horizontal style fixtures, turned 90*, lighting a wall of plants.
The only person, that I'm aware of, who's built a vert LED fixture for traditional donut type vert growth is myself. Will it be counterproductive? Not sure, as I haven't put them through a cycle yet, but they seem promising so far.
I've built a ~100w horizontal seedling/clone light, a ~200w vertical veg light, and most of a ~480w vertical flower light. I should (FINALLY) be receiving the 480w driver today, so I can finish and fire up the flower fixture. So far the clone light and vert veg light are working well. The vert veg light is actually being tested flowering a couple of plants in a 4x4 tent at the moment, and they're looking good; pretty blinding. The 480w light should be even better!
I don't have any pics up yet, but if you'd like, you can check out my thread in LED section. There are diagrams and plans that will at least give you an idea of how to make a DIY vert LED fixture for traditional vert style growing.
Here's the link to my thread: https://www.icmag.com/ic/showthread.php?t=341924
I hope this helps satisfy your curiosity, and sparks some ideas for your own setup.